Manufacture of mixed alkyl tetraalkyllead products



United States Patent M 3,231,510 MANUFACTURE OF MIXED ALKYLTETRAALKYLLEAD PRODUCTS Rex D. Closson, Royal Oak, Mich., assignor t0Ethyl Corporation, New York, N.Y., a corporation of Virginia No Drawing.Filed May 1, 1962, Ser. No. 191,421

6 Claims. (Cl. 252386) This invention relates to the manufacture oftetraalkyllead compounds. More particularly, the invention relates tothe manufacture of the so-called mixed alkyllead compounds, that is,those compounds of lead wherein each molecule contains dissimilar alkylgroups.

It has long been known that the production of compositions having mixedalkyllead compounds can be attained by a redistribution of two or moredifferent tetraalkyllead compounds. The tetraalkyllead compounds may bedifferent in having different alkyl groups, but each compound havingonly one specific alkyl group. Alternatively, each compound can havedifferent alkyl groups, but the compounds would differ one from theother in the numbers of the different alkyl groups present in eachcompound.

For example, it has been appreciated that tetraethyllead andtetramethyllead could be interreacted under appropriate conditions, andwith the aid of a catalyst, to achieve a product having a plurality ofmixed alkyllead compounds, viz., a plurality of compounds having bothmethyl and ethyl groups thereon. Thus, in the interreaction oftetraethyllead and tetramethyllead, in equimolar proportions, theproduct obtained will contain minor amounts of both tetraethyllead andtetramethyllead, but the predominant components will betriethylmethyllead, diethyldimethyllead and ethyltrimethyllead. Anotherillustration of a redistribution reaction is the reaction of a mixtureof, for example, trimethylethyllead and methyl triethyllead.

A process for carrying out the above type reactions has been disclosedin Calingaert et al. Patent 2,270,108. According to that patent, achemical catalyst is necessary, and the catalysts employed include, forexample, diethyl zinc, zinc fluoride, mercuric chloride, borontrifluoride, dimethyl aluminum chloride, zirconium chloride, phosphorustrichloride, and ferric chloride. In other words, all the catalystsheretofore known have been halogen containing compounds or certainorganometallic compounds such as diethyl zinc.

Certain alkyl-halogen compounds of aluminum are quite effectivecatalysts, such as methyl aluminum sesquichloride. Halides such asaluminum chloride, and particularly boron trifluoride, or the etheratethereof, are quite successful. However, processes catalyzed bychemically active catalysts such as above listed exhibit certaindeficiencies in commercial operation. in particular, commercialoperations have suffered because the catalysts employed tend to cause adegradation of a minor quantity of the lead tetraalkyl charged, whichrepresents a loss in that the degradation products must be removed fromthe final product. Further, certain of the prior art catalysts are quitehazardous and difficult to handle. For example, boron trifluoride is,itself, a very toxic material, and in addition, is a gaseous material.It is recognized, of course,

3,231,510 Patented Jan. 25, 1966 ICC that the tetraalkyllead feedmaterials and the mixed alkyllead products to be obtained are themselvestoxic materials, but obviously it is undesirable to be forced to handleyet an additional toxic material. Another deficiency of the priortechniques arises from the fact that the preferred chemical catalystsheretofore known react with certain minor components present in thefinal products in which the mixed alkyllead compounds appear. Thus, astetraalkyllead compounds are employed in antiknock motor fuel additivesin which a dye is added, it would be quite desirable if such dye couldbe added at the very beginning, Without requiring an additional blendingoperation after the redistribution of two tetraalkyllead materials.However, this has not been feasible in the past because the prior artredistribution catalysts react with or adsorb the dye and destroy itseffectiveness.

The principal object of the present invention is to provide a new andhighly efficient process for the redistribution of at least twodifferent tetraalkyllead compound feeds to provide a desired mixed alkyltetraalkyllead product. A more particular object is to provide such aprocess wherein the redistribution of the alkyl groups necessary is notaccompanied by any significant loss of lead value, viz., loss byconversion of the lead from a lead alkyl moiety to anothernon-utilizable lead compound. Still another object is to provide aneffective redistribution process which does not employ chemically activecatalysts. By this is meant that no catalyst is employed which issusceptible of undergoing a chemical reaction with the tetraalkylleadcomponents themselves or components present with the tetraalkylleadmaterials. Other objects Will appear hereinafter.

The present invention comprises contacting at least two differenttetraalkyllead compounds, susceptible to redistribution of the alkylgroups, with a high surface inorganic agent selected from the groupconsisting of activated aluminosilicate clays, synthetic zeolites,zeolite, activated silica and activated alumina. The contacting iscontinued for a sufficient period of time to achieve the desired degreeof redistribution, which, occasionally, is deliberately selected at alevel below the potential maximum or theoretical redistribution. Thetemperature of operation is not critical, although, of course,temperatures above the decomposition temperature of the components areto be necessarily avoided. A great degree of flexibility in the mode ofcontacting and in the time of contacting is permissible, according tothe results desired.

The inorganic high surface agents employed do not exhibit preciselydefinable chemical characteristics known to be responsible for theeffectiveness of the process. Inorganic materials having high surfaces,are not always effective. Thus, diatomaceous earth, and activated carbonhave been found to be virtually ineffective for the desired reaction.Among the modes of contacting which can be employed are batch operationsin which a selected quantity of the high surface inorganic material insubdivided form is added to the raw mixture, stirring is provided andredistribution Will occur to the desired extent in a satisfactory periodof time, depending upon the concentration of material employed. Anotherhighly effective mode of contacting involves passing the feed stockthrough a stationary column or bed of the material, either in downflowor upflow. The rates are adjusted as desired to provide the desireddegree of redistribution. Batch, semi-batch, and continuous processingtechniques, are of course readily available. For most applications, theuse of a stationary bed of the high surface material and percolation ofthe feed materials therethrough, is highly effective.

The invention is not limited to the use of highly concentratedtetraalkyllead feed components, but in fact can be used to process twodifferent antiknock compositions each having a single tetraalkylleadcomponent therein, as well as halogenated hydrocarbon materials employedas scavengers and other constituents found in commercial antiknockliquid compositions.

Example 1 Into a 500 milliliter three neck round bottom flask, providedwith mechanical stirrer, a reflux condenser and a dropping funnel werecharged 11.8 grams of an activated clay having the following approximatecomposition.

Component: Weight percent SiO 74 A1 17.5 MgO 4.5 F2O3 1.4

Also charged were 64.7 grams of tetraethyllead and 53.5 grams oftetramethyllead, thus providing a TEL:TML mole ratio of-1.2: 1.

The flask was heated at about 55 to 65 C. for two hours while stirringvigorously. The activated clay provided was in the form of subdividedparticles, predominantly all passing a 10 mesh screen.

At the end of the above reaction period, the contents of the flask werecooled and filtered to obtain a solidsfree filtrate.

The filtered liquid was then distilled at a reduced pressure, initially50 millimeters of mercury, and dropping over a distillation period ofseveral hours, to about 5 millimeters mercury pressure. The distillationcurve and the volume of distillate fractions showed the followingcomponents were present in the molal concentrations given below.

Compound: Mole percent Tetramethyllead 2.7 trimethylethyllead 20.1Dimethyldiethyllead 41.7 Methyltriethyllead 27.7 Tetraethyllead 2.8

The distillate composition reported above was for a recovery of over 90weight percent, a small amount being lost in handling and a residue ofabout 5 percent being not distilled or analyzed. Generally, theforegoing experiment showed approximately complete redistribution of thealkyl groups.

To illustrate the operation of the process using a stationary bedreaction zone, the following example is illustrative.

Example 2 A glass column was packed with activated clay having the samecomposition as the clay used in Example 1, but confined to the -20 meshfraction. The bed employed was about 8 inches in depth. An equimolalmixture of tetraethyllead and tetramethyllead, accompanied by toluene tothe extent of about 20 weight percent of the tetramethyllead, was fed tothe top of this column and allowed to flow therethrough at roomtemperature, of about 24 C. The mixture was fed at the rate of about 2(1.92.4) grams per gram of catalyst per hour, the flow rate beingcontrolled by withdrawal at the bottom. Operation was continued for a 30hour period, at which time about 66 grams of feed had been passed forevery gram of the clay bed. Complete redistribution of the entire feedwas ac complished, as shown by the following analysis of the dischargedmaterial.

Compound: Mole percent Tetramethyllead, TML 6.9 Trimethylethyllead, MeEtPb 20.2 Dimethyldiethyllead, Me Et Pb 40.7 Methyltriethyllead, MeEt Pb26.6 Tetraethyllead, TEL 5.6

Without changing the clay charge in the column, an additional supply offeed was passed through under the same conditions for an additional 28hours, and analysis of the product showed that the activity wasmaintained and complete redistribution, according to approximately theforegoing analysis, was obtained.

The theoretical complete redistribution products from a feed havingequimolal proportions of tetraethyllead and tetramethyllead is asfollows.

Compound: Mole percent TML 6.25

Me EtPb 25.0 lVIe Et Pb MeEt Pb c 25.0 TEL 6.25

The foregoing theoretical distribution assumes equivalent mobility ofeach alkyl group present. This assumption is not fully accurate, anddistributions containing more than the 37.5 mole percent of thedimethyldiethyllead component are frequently attained. About the highestconcentration of this component which can be obtained is of the order ofabout 110 percent of the above listed molal concentration. For referencepurposes herein, the term percent redistribution is adopted asequivalent to a molal concentration of 37.5 percent, as in the abovetable.

A particular benefit of the improved process is the ability toaccomplish the desired redistribution in the presence of othercomponents of the desired final antiknock mixtures for which thealkyllead is intended. This is highly advantageous inasmuch as itprovides the opportunity of providing, rapidly, individual, mixedalkyl-tetraalkyllead antiknock compositions according to rapidlychanging needs, but using only two antiknock mixtures as inventorystocks. It is therefore now possible to provide, from two previouslyblended antiknock mixtures a mixed alkyl tetraalkyllead containingantiknock composition tailored for the needs of a particular fuel,without maintaining an inventory of such a composition. Morespecifically, by way of illustration, it is now possible to maintain aninventory of, for example, a tetraethyllead containing antiknockmixture, and a tetramethyllead antiknock mixture, with all the usualother constituents present, and to establish directly from suchmixtures, new antiknock mixtures having a desired mixed methyl-ethyltetraalkyllead content, without the necessity of maintaining aninventory of the latter, or without the necessity of reblending orredyeing. The following example illustrates a redistribution ofcommercial but non-dyed TML (tetramethyllead) and TEL (tetraethyllead)antiknock liquids.

Example 3 The charge in this operation was of the following composition.

In this mixture, the tetraethyllead and tetramethyllead wereapproximately in equimolal quantities and the halogenated ethanecomponents were in the proportions approximating a commercial mixture.The mixture was fed through a column corresponding to that used inExample 2 above for an extended period with shown on the followingtable:

the results Product, mole percent Rate, g./(g. Time solids) (hr.) (hr.)

TML Me EtPb Me2Et2Pb MeEtaPb TEL 1 spot sample.

From the foregoing data, it is seen that the process is equally asefifective when the feed streams include, not only the tetraalkylleadcompounds to be redistributed, but also components, particularly halogencontaining compounds, which are provided for a final antiknock liquidcomposition. The practical implications of this are, of course,extremely important as already indicated. Thus, it is possible toprovide antiknock liquid compositions, wherein only one tetraalkylleadcompound is present, but at the same time two such compositions can bereadily treated or reacted together to give at will mixed alkyltetraalkyllead components to serve a particular need.

In addition to being unaffected by the presence of haloethane compounds,as shown by Example 3 above, the process is also highly advantageous inthat it does not affect the color of the materials being processed.This, also, is quite important, as tetraalkyllead antiknock compositionsare provided with a strong dye so that leaks which can possibly occurare readily detectable, and the final fuel composition can beidentified.

I Example 4 The operation of Example 3, above, was repeated except thatthe antiknock liquids provided were both dyed with a water insolubleorange dye, phenyl azo 2-napthyl, in sufficient concentration to providea recognized stain or color intensity in the final fuels. The operationwas carried out as :before, and vapor phase chromatography analysisagain showed that approximately complete redistribution had beenachieved. In addition, the intensity of the orange color was the same inthe treated product as in the feed materials. Similar operations werecarried out with a feed containing a blue dye, with equal success.

As already stated, instead of the activated clay used in the foregoingexamples, certain other inorganic, relatively high surface materials arealso. quite effective, as is shown by the following examples.

Exam pie 5 In this operation, the same operating technique as in Example2 was applied, except that the contact material employed was anactivated alumina (Kaiser Chemical grade XA281) with an average porediameter of 40 Angstrom units. The feed mixture provided in this casewas an equimolal mixture of tetraethyllead and tetramethyllead,accompanied by dry toluene in the proportions of about 20 weight percentbased on the tetramethyllead. The feed was percolated through an 8 inchcolumn at the rate of approximately one gram per hour per gram ofsolids, and this operation was continued for approximately 5 hours.Analysis of the product showed the following concentration of alkylleadcomponents.

Example 6 In this operation, the same procedure as in the above examplewas followed, except that the rate of feed was (Fisher ScientificCompany) which was screened to pass a 28 mesh screen and be retained ona 200 mesh screen. The operation was continued for about six hours, anda composite analysis of the products shows the following tetraalkylleadcomponent distribution.

Example 7 The same procedure as in Example 3 was followed, except that asynthetic zeolite, having the approximate water free composition Na O-A1O -2SiO was used. Such materials have a pore diameter of about 4.2Angstrom units, and internal surface area of from 700 to 800 squaremeters per gram. Preparatory methods are described in Patents2,882,243-4. About 130 g. of synthetic zeolite were used. Contacting waswith 10, 20 and gram portions, at the rates of 460, 19 and 4 grams offeed per gram of solids per hour. Redistribution to about 102 percentwas obtained.

When natural zeolites are substituted for the acid activated clays,activated silicas, activated alumina, and synthetic zeolite used in theabove examples, similar results are obtained.

When the length of the column is approximately doubled, and the grossfeed rate is maintained the same, substantially complete redistributionis achieved.

The life of the contacting solids employed in the process is very high,so that regeneration is not normally an economic necessity. However,regeneration can be achieved readily by steaming the solids, andthereafter d-rying at a temperature of about 100-125 C., preferably withan inert gas being passed through the solids.

The following example illustrates operation on a substantial scale andshows the effect of temperature variation.

Example 8 A three inch standard steel pipe reactor was charged withabout 12 pounds of activated clay, having the composition recited inExample 1, the clay being in the 10-20 mesh size. (One commercial sourceof such clay is Filtrol grade 24, obtainable from Filtrol Corporation.)

The feed to the reactor was a blend of tetramethyllead andtetraethyllead containing antiknock mixtures, having about 20 weightpercent toluene, based upon the tetramethyllead, and dichloroethane anddibromoethane in the molal proportions of 1.0 mole and 0.5 mole,respectively, per mole of the alkyllead constituents. The antiknockmixture also contained orange dye and minor amounts of other components.The feed was passed through the bed in an upward manner, so that thecolumn of solids was flooded at all times. The rate of feed was adjustedto provide at least 100 percent redistribution. Temperatures were variedduring portions of the operation and feeds were maintained at themaximum permissible at such temperatures, as shown by the followingtable.

Temperature, C.: Feed rate (lb. of

solids) (hr.)

When operating at 30 C., it was found that after t-reating approximately119 pounds of mixed feed per pound of a solid that the activityappreciably decreased. At the other temperatures shown, no limit ofactivity Was reached. A total of 2,140 pounds of feed was processed perpound of clay solids with no falling-off in conversion and virtuallycomplete recovery of the tetraalkyllead was obtained.

The same operation was carried out, but instead of having equimolarproportions of tetramethyllead and tetraethyllead in the feed,proportions were adjusted to one mole of tetramethyllead per three oftetraethyllead, and three moles of tetramethyllead per one mole oftetraethyllead, and substantially complete redistribution was obtainedin each instance.

Although tetraethyllead and tetramethyllead are the most significanttetraalkyllead source materials at the present time, the process isequally applicable to other alkyllead compounds. Thus, when feedmixtures containing tetra-n-propyl and tetraethyllead, tetraisobutylleadand tetraethyllead, tetra-n-butyllead and tetraethyllead andtetra-n-propyllead and tetramethyllead are substituted in the foregoingexamples, corresponding results are achieved.

As illustrated by the examples given above, temperatures can be ordinaryambient temperatures if desired, but in crease of the temperature to85-90 C., illustratively, provides a substantial increase in capacity.However, the temperature is not critical as shown by the resultsobtained. Temperatures so high as to approach the thermally unstablerange of the tetraalkyllead compounds fed should be avoided. Thconcurrent presence of halogenated hydrocarbon components and oftoluene, as in numerous of the examples above, reduces thermaldecomposition.

In the foregoing examples the high surface solids are employed pure,i.e., Without any adulterants or additives. In certain instances it isdesirable to provide additional inert materials or fillers such as sandetc. In addition, it will be understood other chemical constituents maybe present or combined in certain of the high surface inorganic solidswithout having a deleterious efiect on the performance thereof.

The precise size of the particles of solids employed is not critical.The significant feature of the materials is in the finite crystalscomposition and arrangement, rather than in the gross particle size. Itnecessarily will be clear, however, that the use of physical aggregatesof too fine a particle size will result in quite slow flow inembodiments of the process characterized by the flow of the feedmaterial through a solid stationary bed of the material. On the otherhand, embodiments, such as Example 1 in which the solids are added to astirred liquid mixture of the material being processed, and a batchredistribution is carried out, permit very fine materials to beemployed. These are then readily filterable by conventional, highquality filtration operations. Generally, it is preferred that theparticle aggregates in 8 fixed bed operation shall be at least retainedon a 200 mesh, and desirably not greater than a ten mesh. An even morepreferred particle range size for such embodiments is 10 to 20 meshparticles.

As previously described, the feeds to the process, when using twodifferent tetraalkyllead compounds Where the alkyl groups on one of suchcompounds are identical in the compound, can vary widely. Equimolalproportions are most customary. However, the feed stock can be varied asdesired according to the desired proportions of the different alkylgroups in the final product. In the case of products having methyl andethyl alkyl groups, the usual range of feed proportions is from about0.2 to 4 moles of tetramethyllead per mole of tetraethyllead.

I claim:

1. A process for the redistribution of at least two differenttetraalkyllead compounds susceptible to redistribution comprisingcontacting said compounds at a temperature below the temperature ofdecomposition with a high surface inorganic solid selected from thegroup consisting of activated alurninosilicate clays, syntheticzeolites, zeolites, activated silicas and activatedaluminas for a timesufficient to redistribute the alkyl groups.

2. The process of making an antiknock liquid having the followingtetraalkyllead components therein:

tetramethyllead trimethylethyllead dimethyldiethylleadmethyltriethyllead tetraethyllead and in addition thereto otherconstituents of an antiknock liquid including halogenated hydrocarbonscavenger components, dye, and inert hydrocarbons, said processcomprising mixing tetramethyllead and tetraethyllead and otherconstituents of antiknock liquids including halogenated hydrocarbonscavenger components, dye and inert hydrocarbons, the tetramethylleadbeing in proportions of from 0.2 to 4 moles per mole of tetraethyllead,and contacting the so-formed mixture at a temperature of not over about90 C. with inorganic high surface solids consisting predominantly ofparticles passing a ten mesh screen and being retained on a 200 meshscreen and being selected from the group consisting of activatedaluminosilicate clays, synthetic zeolites, zeolites, activated silicasand activated aluminas, and the contacting being at a rate of 1 to about500 parts by weight per part of solids per hour.

3. The process of claim 2 in which the inert hydrocarbons are dry.

4. The process of claim 3 wherein the contacting is carried out at atemperature of from about 50 C. to about C.

5. The process of claim 3 further characterized by said inorganic highsurface solids being substantially water-free.

6. The process of claim 1 further characterized by said inorganic highsurface solids being essentially dry.

References Cited by the Examiner UNITED STATES PATENTS 2,407,307 9/1946Linch 260-437 TOBIAS E. LEVOW, Primary Examiner.

ABRAHAM H. WINKELSTEIN, Examiner.

1. A PROCESS FOR THE REDISTRIBUTION OF AT LEAST TWO DIFFERENTTETRAALKYLLEAD COMPOUNDS SUSCEPTIBLE TO REDISTRIBUTION COMPRISINGCONTACTING SAID COMPOUNDS AT A TEMPERATURE BELOW THE TEMPERATURE OFDECOMPOSITION WITH A HIGH SURFACE INORGANIC SOLID SELECTED FROM THEGROUP CONSISTING OF ACTIVATED ALUMINOSILICATE CLAYS, SYNTHETIC ZEOLITES,ZEOLITES, ACTIVATED SILICAS AND ACTIVATED ALUMINAS FOR A TIME SUFFICIENTTO REDISTRIBUTE THE ALKYL GROUPS.